Home Range Shape Research Articles

Where to fly? Landscape influences on the movement and spatial ecology of a threatened apex predator

Effectively managing apex predators in human-modified landscapes poses considerable challenges. Habitat fragmentation disperses resources across wider expanses and undermines the ability of apex predators to reach isolated habitat patches as they traverse multi-tenured landscapes comprising unsuitable habitat. Understanding a species response to landscape configuration is key to informing effective management strategies, particularly for threatened, mobile and ecologically important species like apex predators. Here we use GPS tracking data collected from 37 powerful owls (Ninox strenua), an Australian threatened apex predator that occurs across the urban-agricultural-forest gradient, to investigate how landscape characteristics influence their spatial and movement behaviour. We demonstrate that as habitat fragmentation increases, the spatial requirements of powerful owls expand, their home-range shape becomes more intricate and individuals travel further each night, significantly adjusting their movement behaviours and spatial configurations to connect remaining habitat. Landscapes with unified and connected habitats, on the other hand, have smaller spatial requirements, likely due to greater habitat availability that minimises competition for essential resources. This facilitates the establishment of smaller home-ranges and consequently, the occurrence of more territories. Interestingly, landscape characteristics did not influence sequential nightly visitation behaviour, suggesting that powerful owls across all landscape types visit different portions of their home-range each night to exert an unpredictable hunting strategy regardless of local landscape conditions. Our research highlights the importance of integrating the influence of local landscape features and visitation behaviours into decision-making processes. This integration is crucial for informing effective conservation strategies aimed at supporting apex predator survival in disturbed landscapes.

Influence of biotic and abiotic factors on home range size and shape of invasive wild pigs (Sus scrofa).

Determining factors influencing animal movements at a temporal scale that is similar to that at which management actions are conducted (e.g. weekly) is crucial for identifying efficient methods of wildlife conservation and management. Using global positioning system (GPS) data from 49 wild pigs in the southeast United States, we constructed weekly 50% and 95% utilization distributions to quantify the effects of biotic and abiotic factors on weekly core area and home range size, as well as home range shape. We found vegetative composition (i.e. proportion of bottomland hardwoods), season (based on forage availability), meteorological conditions (i.e. temperature and pressure), and sex influenced wild pig weekly home range and core area size, while vegetative composition (i.e. proportion of upland pines) and landscape features (i.e. distance to streams) also were important factors influencing home range shape. At close distances to streams, wild pigs had more elongate home ranges when their home ranges comprised less upland pine habitat; however, farther from streams, there was no change in home range shape across fluctuating proportions of upland pines. These results demonstrate that fine-scale wild pig home ranges and movements are pliable from week to week and influenced by several habitat, landscape, and meteorological attributes that can easily be quantified from available land use and meteorological databases. These findings are important for designing monitoring studies, identifying high risk zones for disease transmission, planning response to disease emergence events, and allowing more effective and efficient short-term management planning.

Sex-specific effects of reproductive season on bobcat space use, movement, and resource selection in the Appalachian Mountains of Virginia.

Across taxa, sex-specific demands vary temporally in accordance with reproductive investments. In solitary carnivores, females must provision and protect young independently while meeting increased energetic demands. Males seek to monopolize access to females by maintaining large territories and defending them from other males. For many species, it is poorly understood how these demands relate to broad-scale animal movements. To investigate predictions surrounding the reproductive strategies of solitary carnivores and effects of local conditions on bobcat (Lynx rufus) spatial ecology, we examined the effects of sex and reproductive season on home range size, movement rate, and resource selection of bobcats in the central Appalachian Mountains. Male seasonal home ranges were approximately 3 times larger than those of females (33.9 ± 2.6 vs. 12.1 ± 2.4 km2, x±SE), and male movement rates were 1.4 times greater than females (212.6 ± 3.6 vs. 155 ± 8.2 m/hr), likely reflecting male efforts to maximize access to females. Both sexes appear to maintain relatively stable seasonal home ranges despite temporally varying reproductive investments, instead adjusting movements within home ranges. Males increased movements during the dispersal period, potentially reflecting increased territoriality prior to breeding. Females increased movements during the kitten-rearing period, when foraging more intensively, and frequently returning to den sites. Both sexes selected home ranges at higher elevations. However, females selected deciduous forest and avoided fields, whereas males selected fields and avoided deciduous forest, perhaps explained by male pressure to access multiple females across several mountain ridges and higher risk tolerance. Seasonal changes in home range selection likely reflect changes in home range shape. Increased female avoidance of fields during kitten rearing may indicate female avoidance of presumably resource rich, yet risky, fields at the time when kittens are most vulnerable. Our results indicate that while reproductive chronology influences the spatial ecology of solitary carnivores, effects may be constrained by territoriality.

Life in linear habitats: the movement ecology of an endangered mammal in a peri‐urban landscape

AbstractAnimal movement can be significantly altered in human‐dominated landscapes such as urban and peri‐urban areas, where habitat is often fragmented and/or linear. Knowledge regarding how wildlife respond to anthropogenic change is vital for informing conservation efforts in such landscapes, including the design of nature reserves and wildlife corridors. To better understand how threatened species persist and behave within human‐dominated landscapes, we examined the home range and space use of the nationally endangered southern brown bandicoot Isoodon obesulus obesulus in peri‐urban Melbourne, Australia’s second‐largest city. Specifically, we examined whether: (1) bandicoots were confined to linear strips of remnant vegetation or also made use of the broader highly modified landscape matrix; (2) the configuration of the linear vegetated strips affected home range shape; and (3) home range area differed between bandicoots living in linear strips and those in larger remnant habitat patches. We found that: (1) 71% of adult males and 33% of adult females used the matrix, but non‐dispersing juveniles were entirely confined to the linear strips; males also travelled greater distances into the matrix (away from the vegetated strips) than females; (2) bandicoots had longer home ranges in narrower strips and males had longer home ranges than females; and (3) home range area for both sexes was smaller in linear strips than has been recorded in other studies in larger remnant habitats. Our study highlights the importance of retaining narrow, fragmented and modified vegetation to accommodate threatened biodiversity within human‐dominated landscapes, but suggests the surrounding matrix may also offer important resources for adaptable species, such as bandicoots. Supporting off‐reserve conservation of biodiversity in novel ecosystems is increasingly pertinent in our rapidly urbanizing world.

Modified home range kernel density estimators that take environmental interactions into account

BackgroundKernel density estimation (KDE) is a major tool in the movement ecologist toolbox that is used to delineate where geo-tracked animals spend their time. Because KDE bandwidth optimizers are sensitive to temporal autocorrelation, statistically-robust alternatives have been advocated, first, data-thinning procedures, and more recently, autocorrelated kernel density estimation (AKDE). These yield asymptotically consistent, but very smoothed distributions, which may feature biologically unrealistic aspects such as spilling beyond impassable borders.MethodI introduce a semi-parametric variant of AKDE designed to extrapolate more realistic home range shapes by incorporating movement mechanisms into the bandwidth optimizer and into the base kernels. I implement a first approximative version based on the step selection framework. This method allows accommodating land cover selection, permeability of linear features, and attraction for select landscape features when delineating home ranges.ResultsIn a plains zebra (Equus quagga), the reluctance to cross a railway, the avoidance of dense woodland, and the preference for grassland when foraging created significant differences between the estimated home range contours by the new and by previous methods.ConclusionThere is a tradeoff to find between fully parametric density estimators, which can be very realistic but need to be provided with a good model and adequate environmental data, and non-parametric density estimators, which are more widely applicable and asymptotically consistent, but whose details are bandwidth-limited. The proposed semi-parametric approach attempts to strike this balance, but I outline a few areas of future improvement. I expect the approach to find its use in studies that compare extrapolated resource availability and interpolated resource use, in order to discover the movement mechanisms that we need to improve the extrapolations.

Shape complexity of space used by American black bears influenced by sex and intensity of use

Disentangling the complexities that influence animal space use poses substantial challenges based on decision trade-offs and constraints imposed on animals. Optimal decisions suggest that the spatial complexity of home-range shapes should be inversely related to energy conservation and fitness. Hence, the most beneficial shape should be the circle. We evaluated whether shape complexity (i.e., an index of circularity) of home ranges was influenced by two extrinsic (spatial heterogeneity, preferred habitat [i.e., deciduous forest]), and three intrinsic (sex, season [breeding, non-breeding], intensity of use) factors, with intensity of use indexed as contours containing core and peripheral areas. We estimated utilization distributions of 39 radiomarked adult American black bears (Ursus americanus), a habitat generalist, using fixed-kernel techniques and estimated 50% (core area) and 95% (peripheral area) contours. We fit a set of 47 models using linear modeling and ranked models using small-sample Akaike Information Criterion. Coefficients for the best model were the intrinsic factors intensity of use (reference category=core; 0.118; 95% CL=0.064–0.173), sex (reference=female; 0.105; 95% CL=0.043–0.167), and intercept (0.229; 95% CL=0.186–0.272). Shape complexity was less for core areas than peripheral areas and less for females than males. Considering complex resource selection patterns within a fragmented landscape, both sexes appeared to use energy-maximizing strategies, although the increase in shape complexity for males may be an allometric relationship based on size dimorphism. Our approach supported the phenomenon of optimality as manifested through home-range shape complexity, but we suggest that assessment of this phenomenon for habitat specialists may yield different results, including the potential importance of intrinsic factors based on more restrictive limiting factors.

Testing the consistency of wildlife data types before combining them: the case of camera traps and telemetry.

Wildlife data gathered by different monitoring techniques are often combined to estimate animal density. However, methods to check whether different types of data provide consistent information (i.e., can information from one data type be used to predict responses in the other?) before combining them are lacking. We used generalized linear models and generalized linear mixed-effects models to relate camera trap probabilities for marked animals to independent space use from telemetry relocations using 2 years of data for fishers (Pekania pennanti) as a case study. We evaluated (1) camera trap efficacy by estimating how camera detection probabilities are related to nearby telemetry relocations and (2) whether home range utilization density estimated from telemetry data adequately predicts camera detection probabilities, which would indicate consistency of the two data types. The number of telemetry relocations within 250 and 500 m from camera traps predicted detection probability well. For the same number of relocations, females were more likely to be detected during the first year. During the second year, all fishers were more likely to be detected during the fall/winter season. Models predicting camera detection probability and photo counts solely from telemetry utilization density had the best or nearly best Akaike Information Criterion (AIC), suggesting that telemetry and camera traps provide consistent information on space use. Given the same utilization density, males were more likely to be photo-captured due to larger home ranges and higher movement rates. Although methods that combine data types (spatially explicit capture–recapture) make simple assumptions about home range shapes, it is reasonable to conclude that in our case, camera trap data do reflect space use in a manner consistent with telemetry data. However, differences between the 2 years of data suggest that camera efficacy is not fully consistent across ecological conditions and make the case for integrating other sources of space-use data.

Using simulation to compare methods for estimating density from capture–recapture data

Estimation of animal density is fundamental to wildlife research and management, but estimation via mark–recapture is often complicated by lack of geographic closure of study sites. Contemporary methods for estimating density using mark–recapture data include (1) approximating the effective area sampled by an array of detectors based on the mean maximum distance moved (MMDM) by animals during the sampling session, (2) spatially explicit capture–recapture (SECR) methods that formulate the problem hierarchically with a process model for animal density and an observation model in which detection probability declines with distance from a detector, and (3) a telemetry estimator (TELEM) that uses auxiliary telemetry information to estimate the proportion of animals on the study site. We used simulation to compare relative performance (percent error) of these methods under all combinations of three levels of detection probability (0.2, 0.4, 0.6), three levels of occasions (5, 7, 10), and three levels of abundance (10, 20, 40 animals). We also tested each estimator using five different models for animal home ranges. TELEM performed best across most combinations of capture probabilities, sampling occasions, true densities, and home range configurations, and performance was unaffected by home range shape. SECR outperformed MMDM estimators in nearly all comparisons and may be preferable to TELEM at low capture probabilities, but performance varied with home range configuration. MMDM estimators exhibited substantial positive bias for most simulations, but performance improved for elongated or infinite home ranges.

Home range area and shape of yellow-bellied marmots

Home range is the area that marmots use to obtain food and burrows necessary for growth, reproduction and survival. During regular censuses, the position of each marmot was recorded as a pair of coordinates from a calibrated grid overlain on a photograph of the colony site. Home range area was calculated as the product of the area of a grid square multiplied by the number of grid squares a marmot utilized. Clearly identified excursions were not included in the calculation of area. Shape was determined as the outline of the home range. The analysis included 24 years, four ages, two sexes, four colonies, four categories of residency, and whether an individual engaged in excursions. A general linear model ANOVA revealed that year (P > 0.001), age (P > 0.001), residency (P > 0.001), and colony (P > 0.001) significantly affected home range area but that sex (P = 0.373) and excursions (P = 0.312) did not. Shape was affected mainly by topography and the presence of other marmots. Area increased with age: adults < 2-year-olds < yearlings < young. Territorial males had the largest area followed by adult females whose area was larger than that of yearlings. Home range varied among colonies. Young and transients made the fewest excursions; adults, the most. Excursions were more frequent in the largest colonies. Residency was significantly affected by age, colony, sex, and excursions. Dispersers and transients were male-biased; residents were biased toward females and young.

Feasibility of oral rabies vaccination campaigns of young foxes (Vulpes vulpes) against rabies in summer

Oral vaccination of foxes (Vulpes vulpes) against rabies has been shown to be highly effective. Several baiting strategies to increase vaccination coverage of the target population have been developed. For example, to increase the vaccination coverage of the young fox population before dispersal an additional summer vaccination campaign has been suggested. The effectiveness of such a campaign was evaluated using field data on home range size and shape of young foxes and a simulation model for aerial bait distribution. The results indicated that the limited ranging behaviour of the young fox population during the summer months severely reduced bait accessibility and consequently such an additional vaccination campaign would be very cost-ineffective.

The influence of competitor density on space use in juvenile striped plateau lizards (Sceloporus virgatus)

Abstract To investigate the role of competitor density in influencing space use patterns of juvenile striped plateau lizards ( Sceloporus virgatus ), a density manipulation experiment was conducted within large (800 m 2 ) field enclosures treated with low (20) and high (60) densities of hatchlings. Enclosures were monitored for 10 months, after which the experiment was replicated. Home range and core area sizes after release of lizards and initial establishment in the fall were significantly reduced in the high-density treatments; fall home range shape, measured as the perimeter-to-area ratio, was significantly reduced in low-density treatments; no significant differences were detected between treatments in core area shape or overlap. During the spring/early summer activity season after the lizard's first winter, no significant differences between density treatments were detected for any of these variables, as enclosure densities had converged between treatments. Individuals in high-density enclosures had increased their space use as competitor density had declined. These results illustrate that competitor density has significant influence on space use by juvenile lizards.

Influence of Gender and Den Type on Home Range Shape for Striped Skunks, &lt;em&gt;Mephitis mephitis&lt;/em&gt;, in Saskatchewan

We investigated gender differences in shape of home ranges for Striped Skunks, Mephitis mephitis, in southcentral Saskatchewan, Canada, during 1993-1994. Data collected on free-ranging Striped Skunks indicated that shape of female home ranges was unaffected by den type (building versus burrow) and was similar to shape of male home ranges. Moreover, type of maternity den did not influence the position of the den within the home range (inside or outside of core area). We conclude that the distribution of Striped Skunks in summer, and the distribution of their foraging activity, are not affected by the availability of anthropogenic den structures.

Habitat Use by Meso-Predators in a Corridor Environment

Red foxes (Vulpes vulpes), raccoons (Procyon lotor), and striped skunks (Mephitis mephitis) are found throughout the United States, wherever there is suitable denning habitat and food resources. Densities of these predators have increased throughout the Intermountain West as a consequence of human alterations in habitat. Within the Bear River Migratory Bird Refuge (hereafter, refuge), in northern Utah, USA, upland nesting habitat for ducks is limited to the levee banks and roadsides. Red foxes, raccoons, and striped skunks, which prey on upland nesting birds, are also abundant on the refuge. We studied red foxes, raccoons, and striped skunks' use of levees and the edges associated with them within a wetland environment. Red fox, raccoon, and striped skunk locations were negatively correlated with distance to the nearest dike (−0.78, −0.69, and −0.45, respectively). Animals incorporated more roads and/or levees into their home ranges than expected by chance (x = 2.6; Z < 0.001); incorporation of levees was greater during the dispersal season than the rearing season (P = 0.03). Skunk home ranges (average size, 3.0 km2) were oriented along roads and levees (P = 0.03), whereas raccoon (average size, 3.6 km2) and fox home ranges (average size, 3.5 km2) were not (P = 0.93, P = 0.13, respectively). Fox home ranges in the refuge were more oblong in shape than reported elsewhere (P = 0.03). However, home-range shapes of raccoons and striped skunks were similar to previous studies (P = 0.84, P = 0.97, respectively). The use of roads and levees within the refuge increases the possible travel distance and penetration of predators into wetland environments. This contributes to increased depredation of waterfowl nests and to decreased recruitment. Managers of similar areas might decrease depredation of waterfowl by disrupting the linear pattern of corridors, thereby decreasing the congestion of animal roads and levees. This would, then, decrease the encounter rates of predators and prey.

Estimation of animal location from radio telemetry data with temporal dependencies

We evaluate the performance of several estimators of animal location when data arise from radio telemetry studies. We assume that error-prone bearings are taken at regular time intervals from known locations, that observations may be frequent enough to introduce temporal dependencies, and that animals remain within well-defined home ranges. We simulated data to examine several factors including home range shape, dependency between successive locations, sample size and strategy, and bearing error. Simulated data, supplemented by data based on actual paths for Rocky Mountain elk (Cervus elaphus nelsoni), were used to evaluate alternative location estimators: Lenth’s maximum likelihood estimator (MLE) that assumes independence; Pace’s moving average version of the MLE that introduces a post hoc dependence in the data; and three estimators from state-space models that explicitly model animal movement and dependencies. The state-space models differed in the assumed model of animal movement and included a simple normal random walk, a variation of the random walk that includes a centralizing parameter, and a discretetime version of the Ornstein-Uhlenbeck model for movement within an elliptical home range. Estimates were evaluated in terms of location error and estimator precision. The independent MLE had the poorest performance under most scenarios, particularly when actual locations were dependent. The centrally biased random walk estimator generally had smallest location errors and best precision, whether or not data displayed dependencies. Rather than assuming independence or discarding observations to achieve independence, estimation of location would be served better by accounting for potential dependencies. Methods based on simple models of animal movement may vastly improve estimates, and models that recognize an animal’s sense of home territory are preferred.

Spatial behaviour of the red fox (Vulpes vulpes) in a rural area of central Italy

Seven foxes (Vulpes vulpes) were studied by radio‐tracking from 3 to 12 months/animal, and a total of 4 005 fixes was made. Seasonal home ranges were calculated using several methods giving a minimum of 29–3 and a maximum of 268.7 ha (100% Minimum Convex Polygon). The land use by the foxes was monitored and the habitat analysed. No uniform home range use was revealed, but several core areas were identified; 1–3 of rest and 1–4 of activity being found, seasonally, in each home range. The distribution of core areas of rest and activity suggested that home range size and shape were determined not only by core areas of activity but also by resting sites. The Kernel centres of rest were localised mainly in natural vegetation (85.1%) and sometimes in cereal fields (12.1%) or in hay‐lofts (2.8%), while those of activity were in anthropic environments (56.1%) as well as in natural vegetation (43–9%), but with seasonal variations. Activity was mainly nocturnal, but interrupted by resting periods. Some individual variations were also revealed in home range size, number of core areas, habitat use and daily activity.

Home-range characteristics and movement patterns of the red-legged pademelon (Thylogale stigmatica) in a fragmented tropical rainforest

Home-range characteristics and movement patterns of five male and eight female red-legged pademelons (Thylogale stigmatica) were studied in north-eastem Queensland between September 1991 and June 1992 using radio-telemetry. In relation to mean body weight, the home range of T. stigmatica was small (mean = 2.26 ha, n = 9), individually variable (range 0.82-3.70 ha) and partitioned into spatially distinct diurnal and nocturnal components. The nocturnal range (mean = 1.00 ha,n = 6) incorporated forest edge and pasture habitat, and was somewhat smaller than the diurnal range (mean = 1.67 ha, n = l0), which was located entirely within the forest. Home-range shape was governed largely by the distance between the diurnal and nocturnal ranges, which in turn was related to physical features within the habitat. Pademelons moved slowly within and quickly between their diurnal and nocturnal ranges. Movement between these areas occurred just after dusk and just prior to dawn. The diurnal rate of movement (m min-1) was generally higher than the nocturnal rate, suggesting that pademelons moved extensively in the forest during the day, and were relatively sedentary whilst on pasture at night.

Home range of the allied rock-wallaby, Petrogale assimilis

The home range and movements of the allied rock wallaby, Petrogale assimilis, a small macropod of the seasonally wet-dry tropics of Queensland, were studied over a 22-month period. There was no significant difference in the size of home ranges (95% isopleth) or core areas (65% isopleth) of males and females. Home ranges were generally elliptical with a mean size of 11.9 ha. Season had a major effect on home ranges. The following measures were all significantly greater in the dry seasons than in the wet seasons: home-range size (larger), home-range shape (more elongate), distance moved by females when feeding (longer), distance between shelter site and home-range centre of activity (longer). Feeding movements of males did not vary seasonally and were as long as dry-season movements of females, suggesting that movements of males are primarily determined by behavioural rather than physiological considerations. The overlap of rock-wallaby home ranges varied little between the sexes or seasons and averaged 38%. Core areas overlapped by an average of 22%; however, feeding adult rock-wallabies rarely met other conspecifics, except their partners. A comparison of the fixes of unpaired wallabies that had overlapping home ranges showed that temporal separation was occurring. In contrast, the home ranges of consort pairs showed extremely high temporal and spatial overlap. Rock-wallabies exhibited strong fidelity to their home ranges. The overlap of the seasonal home ranges and core areas of each individual rock wallaby averaged 68% and 52%, respectively. However, the seasonal home range of a socially immature adult male altered in location and size as he matured socially until it stabilised when he obtained a permanent consort.

Effects of Habitat Patch Shape on Population Dynamics of Meadow Voles (Microtus pennsylvanicus)

The geometry of habitat patches may affect population dynamics due to differences in edge-to-area ratios for patches of different sizes and shapes. We conducted a field experiment replicated over 2 years employing four square (40 by 40 m) and four rectangular (16 by 100 m) habitat patches of equal size (1,600 m2) to determine the effects of contrasting shapes of habitat patches on population dynamics of meadow voles (Microtus pennsylvanicus). We tested the predictions that dispersal rates would be higher, home ranges larger, and population densities lower in rectangular patches compared to square patches. The number of dispersers, but not dispersal rates, was greater in rectangular patches than in square patches only when densities of voles were low. Home ranges were of equal area but different shape in the contrasting shapes of patches. Population density, recruitment, body mass of dispersers, body mass of residents, survival, and age structure were largely unaffected by differences in patch shape. Thus, plasticity of behavior (e.g., changes in shape of home range) appears to have prevented differences in population dynamics between the two patch shapes. We conclude that patch shape does not markedly affect the population dynamics of the meadow vole, and that this species appears to be an edge-tolerant species.

Time and Space Use by Two Common Genets (Genetta genetta) in the Donana National Park, Spain

Viverrids have not been studied in the same detail as other families of carnivores (Eisenberg, 1981). For common genets, Genetta genetta, references to its use of space and time are anecdotal, scarce, and usually included in papers on more general topics. Some studies undertaken in Africa on behavior of free-living Genetta genetta (Ikeda et al., 1983; Waser, 1980) must be attributed to Genetta felina after the taxonomic revision of the genus by Schlawe (1980). In this paper, we present information on patterns of activity, homerange size, habitat use, and daily movements of two common genets radio-tracked between September 1985 and April 1986. The study was conducted at the Doniana National Park, which occupies 550 km2 on the right bank of the mouth of the River Guadalquivir, in SW Spain (ca. 37*N, 630'W). It includes three main biotopes: the marshes or marismas, the scrubland, and the dunes. Usually the marshes are flooded in winter, and they were not used by the genets during this study. There are two main types of scrubland: a dry, xerophytic scrubland vegetated by Halimium sp. and Rosmarinus sp. that reach a height of 1.2 m and with relatively low ground cover, and a dense, mesic scrubland vegetated by Erica sp. and Calluna vulgaris, that may reach 3 m in height and cover the ground completely. In the dunes, there are mobile bare sand dunes and depressions or valleys in between, usually colonized by pine (Pinus pinea) forests. Climate is mediterranean subhumid, characterized by dry, hot summers and mild, wet winters. We radio-tracked a young female (weight, 1,040 g; deciduous dentition) and an adult male (weight, 1,750 g; teeth showing no wear signs). Both were captured in live traps baited with sardines, immobilized by injection of a mixture of ketamine hydrochloride (ketolar) and tiazine hydrochloride (Rompun) and equipped with radio-collars (Wildlife Materials Inc.) with switch sensors. The signal was received by a portable AVM LA-12 receiver. The locations were determined by triangulation from a vehicle. We located the genets at least once an hour during seven 24-h periods, and 155 times at random hours of the day apart from intensive tracking periods. A total of 330 locations was determined. Home-range shape and size were estimated from the independent locations, using the smallest convexpolygon method (Macdonald et al., 1980). To determine the zones of most intense use we represented the utilization distribution (Van Winkle et al., 1973) on 10,000-m2 squares. To estimate hourly activity we used distances traveled at each hourly interval of the 24-h tracking periods. The switch sensor of the radio-collar allowed us to know if the animal was active during independent locations. The daily movements were estimated by adding straight-line distances between 25 consecutive hourly locations and multiplying the results by 1.46, an empirical value obtained by Palomares (1986) while tracking the Egyptian mongoose (Herpestes ichneumon) in the same area. The activity of the adult male was exclusively nocturnal, as is usual in genets (Diicker, 1965; Waser, 1980). None of the 70 locations obtained during daylight hours revealed activity. Nevertheless, the young female was active in 19% of 62 locations made during daylight hours, the percentage increasing to 65% (n = 51) during the night. Previously, Ikeda et al. (1982) reported diurnal activity for a female Genetta tigrina in Ethiopia. The partially diurnal activity of the young female we tracked may be explained by its age, as observations of captive genets by one of us (MD) suggest that nocturnality predominates as animals mature. Also, the animal lived exclusively in a dense heather scrubland, where high concealment could diminish interference competition with larger predators, allowing a relaxation of its schedule of activity. Both genets showed greater activity from sunset to midnight, with a secondary peak of activity by the male just before sunrise (Fig. 1). The home range of the young female from 26 September to 31 December was 1.4 km2. On a monthly basis, however, home-range size was 0.2 km2 in October, 0.7 km2 in November and 1.2 km2 in December,with the number of locations roughly similar for the three months (37, 38, and 47, respectively). These results suggest that the female, probably born in the zone, was increasing its familiar environment, as described by Rowe-Rowe (1970) from a young Genetta rubiginosa kept in captivity.

Home Range in a Patchy Environment: Optimal Foraging Predictions

Optimal foraging rules are used to simulate the home range of a central place forager in an environment with a patchy resource distribution. The model makes the following predictions: (1) Home range size is inversely related to maximum resource density and resource renewal rate. It is positively related to the animal's rate of movement. (2) The optimal home range shape in a patchy environment is elongate rather than circular, with a major to minor axisratio of about 2:1. This agrees well with observed values. (3) The proportion of the total home range used per foraging bout is positively related to the renewal rate of the environment. (4) The tendency of an animal to concentrate its activity in a subregion of the home range (rather than distributing its activity uniformly) will increase with the maximum resource density. This tendency is measured as the ratio of the area which will contain 65% of the occurrences of an animal to the area required to contain 95% of its occurrences. The values of the ratio predicted by this model agree closely with observed values.